Mineral fiber boards are mainly used as building materials. Their main constituent consists of mineral fibers such as glass, rock, slag, ceramics, etc. These mineral fibers, together with the other constituents, are shaped into boards by using known processes and, as a result of the production process, the mineral fibers assume a preferred orientation. A known process for producing such mineral fiber boards is, for example, the so-called wet felt process, which is similar to a process used in paper manufacture, as well as a process for producing boards from a spreadable mass in molds, i.e., so-called cast tiles. British Pat. No. 619,674 discloses a synthetic resin laminate, which contains fibrous materials and in which superimposed layers have fiber directions such that the fibers are at right angles to one another. This is intended to give the laminate the same load bearing capacity in both main directions parallel to the main surfaces.
It is also conventional practice to coat mineral fiber boards or to provide them with an embossed surface structure and with a coloring agent for decoration, in order on the one hand to provide a better appearance if the boards are to be used as a partition or as a ceiling board, and on the other hand to give better acoustic damping.
However, the known mineral fiber boards to not always have adequate mechanical strength characteristics for a number of applications, particularly for high-quality ceiling boards or as acoustic boards. Thus, particularly in the case of cast boards, the bending strength is inadequate, so that the boards break very easily during transportion or installation. A further disadvantage of known boards is that they sag relatively easily in the case of high atmospheric humidity and, in extreme cases, ceiling boards can become detached from the suspension means and can fall to the ground. In order that these disadvantages do not reach serious proportions, known mineral fiber boards, particularly to be used as ceiling boards are only supplied in relatively small sizes, which makes installation more expensive due to the complicated support means and the considerable labor costs.